自體動靜脈廔管(arteriovenous fistula, AVF)為需進行血液透析 (hemodialysis, HD)患者之透析管路首選，因其擁有較長的存活時間及 較少的併發症。但術後廔管成熟化前期，常因初始靜脈直徑不足導致 血流量無法提升，而造成AVF 成熟化失敗。研究指出可於手術時透 過支架置入的方式擴大靜脈直徑，進而提高血流量，可有效提高廔管 成功成熟率。然而市售靜脈支架皆為金屬材質製成，置入血管後將永 久存在於體內，易提高血管內再狹窄和血栓形成等風險，因此臨床上 並不傾向使用金屬靜脈支架以提高廔管成熟率。
本研究使用電腦繪圖軟體結合有限元素法設計生物可吸收聚乳 酸(polylactic acid, PLA)氣球擴張式動靜脈廔管支架，並以旋轉式3D 列印機製作，及進行後續驗證。本研究首先以典型支架結構進行參數 優化，設計出支架3 及支架4 進行驗證，從有限元素模擬結果顯示， 徑向力值分別為0.355N/mm 以及0.328N/mm，然而由於支架擴張完 回彈量過大，僅能將靜脈血管擴張至3.84mm 及3.76mm;因此為了達 成擴張後靜脈血管內徑4mm 的目標，本研究設計一款新型卡扣式動 靜脈廔管支架。其原外徑3mm，在藉由氣球擴張至最大外徑5.4mm 時，其卡扣式結構將限制支架回彈。由有限元素模擬顯示，此新型支 架可提供1.389N/mm 之血管支撐力，並可將靜脈廔管內徑成功擴張至4.6mm。本研究所提出的生物可吸收氣球擴張式支架可提高動靜脈廔管成熟率，以利患者後續進行血液透析療程。

Autogenous arteriovenous fistula (AVF) was the first choice for hemodialysis (HD) patients due to its longer survival time and fewer complications. During the initial stage of fistula maturation, the blood flow could be difficult to increase due to insufficient initial venous diameter, and result in the failure of AVF maturation. According to previous research, it was indicated that the diameter of the vein can be enlarged by means of stent placement during the operation, thereby increasing the blood flow, which can effectively improve the successful maturation rate of fistula. However, the commercially available venous stents were all made of metallic materials. After being implanted into a blood vessel, it will remain permanently in the body, which may increase the risk of endovascular restenosis and thrombosis. Therefore, it is not preferred to use metallic stent to improve the rate of fistula maturation in clinical practice.
In this study, bioabsorbable polylactic acid (PLA) balloon expandable arteriovenous fistula stents were designed using computer graphics software combined with finite element method and fabricated by a rotary 3D printing for subsequent verification. First, conventional stent structure and finite element method were used to design two stents, stent 3 and stent 4, for verification. Simulation results showed that the stent radial forces are 0.355N/mm and 0.328N/mm, respectively. However, due to the large recoil after stent expansion, the final diameters of vein, expended by stents, were 3.84mm and 3.76mm, respectively. Therefore, in order to achieve the goal of dilated vein diameter of 4mm, this study designed a new snap-in type arteriovenous fistula stent. Its original outer diameter is 3mm, and when the balloon expands to a maximum outer diameter of 5.4mm, its snap-in structure will limit the stent’s recoil. Finite element simulation showed that the new stent can provide 1.389N/mm radial force and dilate the inner diameter of the fistula up to 4.6mm. The bioabsorbable balloon expandable stent proposed in this study can improve the rate of arteriovenous fistula maturation and facilitate subsequent hemodialysis treatment.

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